Your argument predicates on the idea that you "NEED" to farm for the supposed BIS to reach an end game, to... what exactly? Quit playing until new content?
Fashion, PvP, prestige items/titles, and chilling with friends has ALWAYS been the true end game in MMOs and similar games from WoW, to GW2, to FFXIV, to Warframe and Destiny, to Maple story and Ragnarok; some have gear treadmills while others have prestige skins. MANY MANY people still play games at gear capped end game for various reasons, regardless of the game; it is not the be all and end all. Especially in this game, where it gives tons of leniency and reasonable side-grades. The "Artificial extension" even if it were true, by your logic would only be the barrier between you playing and not playing, and as it stands right now, you can clear all the content; so... if your only goal is to get to a point where you can stop playing, you're probably already there, or at least not far off after a few things from the new ep5 content.
As an example: the substantial difference between Invade and Ofz arm + back is 10atk, 70HP, and 7PP and that isn't necessary nor substantial enough to carry anyone through content. This is not worth stressing over or getting mad about, especially when the games gonna eventually just let you buy it from players, no RNG involved. And Correct me if I'm wrong JP players, but Ofz doesn't really need to be replaced until you upgrade it to a 13* which means buying it is still value even if BIS gear treadmill was the main thing.
Your subjective view that "the game keeps you playing by engaging in the gear grind" is holding you back and a terrible mindset, that is actually incorrect, and extremely narrow minded. This is moderately true through early and mid game, but there is a wide array of effective endgame setups. For example take Qliphad and Zeinesis weapons which are mediocre compared to Nems and Slaves, and an individual would still be able to chill and sufficiently consider themselves at end game at ep 4, and perfectly capable of clearing all the content.
You're assuming that my motivation, or the motivation of anyone playing this game, is min-maxing, getting that 1% more effectiveness. As you said, "Fashion, PvP, prestige items/titles, and chilling with friends has ALWAYS been the true end game in MMOs..." Well, these prestige items (12* BiS units) are locked behind time based or random events. You go on to contradict yourself in your final paragraph, stating, "Your subjective view that "the game keeps you playing by engaging in the gear grind" is holding you back and a terrible mindset, that is actually incorrect, and extremely narrow minded."
If the "gear grind" is so "incorrect" and "extremely narrow minded," then how do you obtain those "prestige items" that you claim to have "ALWAYS been the true end game in MMOs?"